The present invention relates to a process for preparing a highly active metallocene catalyst supported on polymer bead for olefin polymerization, more specifically, to a process for preparing a highly active metallocene catalyst supported on polymer bead for olefin polymerization, which comprises the steps of suspension-polymerization to obtain polystyrene, conferring a functional group of dialcoholamine on the polymer support to give a functional polymer support and reacting the functional polymer support with a metallocene compound (CpM*Cl3) dissolved in an organic solvent, a metallocene catalyst prepared by the said process and a method for alkylene polymerization by employing the said catalyst.
Metallocene catalyst, an organometallic compound which is used for olefin polymerization, though it has many advantages, has major two problems upon commercial application: First, it is very difficult to control morphology of the polymer produced by employing a homogeneous catalyst, which may cause the flocculation on the wall of a reactor; Secondly, the use of an excess amount of methyl aluminoxane (MAO) as a cocatalyst for maximum activity accompanies an essential step of separating residual aluminum beause the produced polymer contains a large amount of aluminum. Therefore, a homogeneous metallocene catalyst cannot be applied in the gaseous process or the slurry process which is practically applied in the art. To overcome these problems, alternative method was developed, in which a metallocene catalyst was supported on metal oxides such as silica, alumina, etc. to give a heterogeneous metallocene catalyst. However, the said method is aimed to improve the efficiency of a separating process and a manufacturing process and to improve the properties of produced polymer such as molecular weight, melting point, etc., rather than to improve the characteristics of a polymerization reaction.
U.S. Pat. No. 4,808,561 discloses a process for preparing a silica-supported catalyst for use in a gaseous process, and Soga et al. teached olefin polymerization by using a zirconocene catalyst supported on the metal oxide (see: Soga, Markromol. Chem., 194:1745, 1993). Recently, Soga and Frechet proposed a catalyst supported on an organic support, i.e., a gel-type functional polymer of polystyrene whose cation is exchanged (see: Soga, Polymer, 41:4005, 2000; Frechet, Science, 280:270, 1998).
However, the prior metallocene catalysts produced by the conventional methods have a low activity and cannot produce a polymer having the properties of a constant range since the properties of a polymer such as structure, length, etc. may be changed depending on the reaction conditions. Naturally, there have been needs for developing a highly active polymer-supported metallocene catalyst with the increased amount of metallocene catalyst for olefin polymerization, while possessing the excellent material properties such as molecular weight, melting point and so on.
Accordingly, there are strong reasons for exploring and developing an improved process for preparing a metallocene catalyst which has a high activity equivalent to that of a homogeneous catalyst without treatment of co-catalyst and can produce an olefinic polymer having the excellent material properties.
The present inventors have made an effort to solve the problems of conventional processes for preparing highly active metallocene catalysts which are used for preparing an olefinic polymer with the excellent material properties, and found that a catalyst wherein metallocene compound is bonded to a polystyrene having a functional group of dialcoholamine has a high activity without treatment of cocatalyst and can be used for the preparation of an olefinic polymer having excellent material properties.
A primary object of the present invention is, therefore, to provide a process for preparing a highly active metallocene catalyst supported on polymer bead for olefin polymerization.
The other object of the invention is to provide a metallocene catalyst prepared by the said process.
Another object of the invention is to provide a method for polymerization of alkylene by employing the metallocene catalyst.
The process for preparing a highly active metallocene catalyst supported on polymer bead for olefin polymerization which comprises the steps of:
(i) dissolving divinylbenzene, vinylbenzylchloride, and an initiator in an organic solvent, mixing it with a suspension stabilizer of aqueous phase, and carrying out suspension-polymerization at the temperature of 40 to 80xc2x0 C. to obtain polystyrene;
(ii) swelling the polystyrene in dialcoholamine dissolved in an organic solvent at ambient temperature for 1 to 3 days, to give a polymer having a functional group of dialcoholamine; and,
(iii) reacting the polymer with a metallocene compound (CpM*Cl3) dissolved in an organic solvent.
The process for preparing a highly active polymer-supported metallocene catalyst for olefin polymerization of the present invention is illustrated in more detail by the following steps.
Step 1: Obtainment of Polystyrene
Divinylbenzene, vinylbenzylchloride and an initiator are dissolved in an organic solvent, and mixed with a suspension stabilizer of aqueous phase, and suspension-polymerization is carried out at the temperature of 40xc2x0 C. to 60xc2x0 C. to obtain a polystyrene, where toluene is preferably used for the organic solvent and 2, 2xe2x80x2-azobis (isobutyronitrile)(AIBN) is preferably used for the initiator and biozan R, cellosize, boric acid, NaCl or mixture thereof is preferably used for the suspension stabilizer. Degree of cross-linking of the polystyrene preferably ranges from 5% to 75%.
Step 2: Obtainment of Polymer Support
The polystyrene obtained in Step 1 is swelled in dialcoholamine dissolved in an organic solvent at ambient temperature for 1 to 3 days, to give a polymer having a functional group of dialcoholamine, where diethanolamine is preferably used for the dialcoholamine and dioxane is preferably used for the organic solvent.
Step 3: Preparation of Metallocene Catalyst
The polymer obtained in Step 2 is reacted with a metallocene compound (CpM*Cl3) dissolved in an organic solvent, where the metallocene compound contains preferably a metal of Ti, Zr, Hf, etc., and ether or toluene is preferably used for the organic solvent. The polymer support is reacted with a metallocene compound by one of the following two methods: First, the polymer is reacted with the 2 equi. of BuLi to be lithiated, which is reacted with a metallocene compound in ether at xe2x88x9278xc2x0 C. for 6 hr; Secondly, the polymer support is reacted with a metallocene compound in toluene.
The metallocene catalyst prepared by the present invention can be used for the polymerization of alkylene or copolymerization of alkylene and xcex1-olefin. Polymerization of alkylene is performed by adding the metallocene catalyst and aluminoxane as a cocatalyst to alkyene dissolved in an organic solvent and reacting the resultant solution under a condition of 20xc2x0 C. to 80xc2x0 C. and 1 to 15 atm for 300 min. Copolymerization of alkylene and xcex1-olefin is performed in a similar manner as the above except for using a mixture of alkyene and 10 to 1000% (molar ratio, against alkylene) of xcex1-olefin dissolved in an organic solvent. Cocatalyst is preferably used in a molar ratio of Al in the cocatalyst to Ti in supported-catalyst ranges 100 to 10,000.
The metallocene catalyst of the present invention can be used widely for ethylene polymerization, styrene polymerization and copolymerization, while replacing the conventional homogeneous catalysts.
The present invention is further illustrated in the following examples, which should not be taken to limit the scope of the invention.